Power semiconductor devices, methods, and structures with embedded dielectric layers containing permanent charges

Abstract

Power devices using refilled trenches with permanent charge at or near their sidewalls. These trenches extend vertically into a drift region.

What is claimed is: 
     
       1. A semiconductor power device, comprising:
 a current-controlling structure at a first surface of a semiconductor mass; 
 a semiconductive drift region extending down into said semiconductor mass;
 said current-controlling structure and said drift region being jointly connected in series between a first source/drain region at said first surface, and a second source/drain region at a second surface of said semiconductor mass; and 
 
 trenches extending down through said drift region into said semiconductor mass, at least some ones of said trenches being at least partially filled with a trench-filling material which is not an insulator, and which is electrically connected to said second source/drain region; 
 said trenches and said current-controlling structure having completely independent lateral alignment; 
 wherein permanent electrostatic charge is present at sidewalls of said trenches. 
 
     
     
       2. The device of  claim 1 , wherein said trenches and said current-controlling structure have different respective pitches. 
     
     
       3. The device of  claim 1 , wherein the device is unipolar, and said first source/drain region is a source. 
     
     
       4. The device of  claim 1 , wherein the device is a diode, and said first source/drain region is a cathode. 
     
     
       5. The device of  claim 1 , wherein said semiconductor mass is a Group IV semiconductor. 
     
     
       6. The device of  claim 1 , wherein said mass is a die of crystalline semiconductive material. 
     
     
       7. The device of  claim 1 , wherein said trench-filling material is a semiconductive material. 
     
     
       8. The device of  claim 1 , wherein said trench-filling material is made of the same semiconductive material as said drift region. 
     
     
       9. The device of  claim 1 , wherein said trench-filling material is a doped crystalline semiconductive material. 
     
     
       10. The device of  claim 1 , wherein said trench-filling material is a semiconductive material grown by selective epitaxy. 
     
     
       11. The device of  claim 1 , wherein said trench-filling material is a semiconductive material which has approximately the same doping as said drift region. 
     
     
       12. The device of  claim 1 , wherein said trenches are generally shaped as linear slots, and said trench-filling material is semiconductive, and wherein the volumetric doping density of said trench-filling material, times the width of said trenches, is approximately equal to the volumetric doping density of said drift region, times the distance between adjacent ones of said trenches. 
     
     
       13. The device of  claim 1 , wherein said second source/drain region is connected as an anode. 
     
     
       14. A semiconductor power device, comprising:
 a current-controlling structure at a first surface of a semiconductor mass; 
 a semiconductive drift region extending down into said semiconductor mass;
 said current-controlling structure and said drift region being jointly connected in series between a first source/drain region at said first surface, and a second source/drain region at a second surface of said semiconductor mass; and 
 
 trenches extending down through said drift region into said semiconductor mass, at least some ones of said trenches being at least partially filled with a trench-filling material which is not an insulator, and which is electrically connected to said second source/drain region; 
 said trenches and said current-controlling structure having completely independent lateral alignment; 
 wherein said trenches are lined with a dielectric layer which includes immobile ions. 
 
     
     
       15. A semiconductor power device, comprising:
 an array of active device cells, including both an upper array of current-controlling structures, and a lower array of permanently charged trenches within a semiconducting drift region; said trenches individually containing permanent electrostatic charge at or near sidewalls thereof; and 
 a transitional structure surrounding said array, said transitional structure including at least some trenches which are fabricated in the same steps as said trenches in said array, but which have smaller maximum width, and a different ratio of charge density between upper and lower portions of the walls of said trenches. 
 
     
     
       16. The device of  claim 15 , wherein said trenches and said current-controlling structure have different respective pitches. 
     
     
       17. The device of  claim 15 , wherein permanent electrostatic charge is present at sidewalls of said trenches. 
     
     
       18. The device of  claim 15 , wherein said trenches are lined with a dielectric layer which includes immobile ions. 
     
     
       19. The device of  claim 15 , wherein the device is unipolar, and said first source/drain region is a source. 
     
     
       20. The device of  claim 15 , wherein the device is a diode, and said first source/drain region is a cathode.